The antibody response to mice to an optimally immunogenic dose of Escherichia coli 0113 lipopolysaccharide (LPS) displays a cyclic (uscillatory) pattern. Although the development of this cyclic pattern is T cell dependent, it does not appear to involve the formation of auto - anti-idiotypic antibody. In studies designed to identify those factors that contribute to the expression of the cyclic pattern, we observed that the development of immunological memory to LPS also proceeds in a cyclic manner. Since the development of memory is T cell dependent, it appears to play a major role in modulating the magnitude of the antibody response to this antigen. In contrast to the antibody response to LPS, the antibody response to Type III pneumococcal polysaccharide (SSS-III) does not proceed in a cyclic manner; also, it is not possible to demonstrate immunological memory to this antigen. Nevertheless, the expression of suppressor T cell activity, which plays an important role in regulating the magnitude of the antibody response to SSS-III, is expressed in a cyclic manner. Such cycling is due mainly to changes in the rate of proliferation of activated suppressor T cells.